Weather and management crucial to yield and quality

Elton Robinson Farm Press Editorial Staff | Nov 16, 2001

You've selected your cotton varieties and matched them as best you can to soil type and management zones. So what expectations should you have of Mother Nature for the upcoming season? And how can your management skills impact what ends up in the ginned bale?

“Yield is determined by the favorableness of the season,” says Tom Kerby, vice president of technical services, Delta and Pine Land Co., “while fiber length and micronaire are primarily affected by environments at specific times in the season.”

For example, fiber length is determined during the first 21 days of boll development, noted Kerby. “To maximize fiber length, cotton plants need adequate fertility (especially potassium), plenty of soil moisture, a good supply of carbohydrates to bolls from leaves, and warm temperatures in that first three weeks of boll development. Water stress during the early boll development period is the biggest detriment to fiber length.”

Micronaire is directly related to sustained boll development from day 21 until the boll is mature (45 to 55 days depending on temperature), Kerby notes. “If carbohydrates are available throughout this late development period, the fiber will be fully developed (more weight per fiber length equals higher micronaire).

“Typically, early-set bolls are high mike,” noted Kerby. “Late-set bolls are lower mike because carbohydrate supply declines due to lower production by the plant and competition from the older bolls.”

But if temperatures don't drop during late season and other conditions remain favorable, “the plant continues carbohydrate translocation, bringing about high mike.”

“This year, many of the areas of the Mid-South saw favorable fall conditions and the mike levels reflect it. Late-season rains kept leaves active and warm night temperatures allowed for fiber to be fully developed. This resulted in higher-than-expected yields, but was accompanied by higher-than-expected micronaire.

“This situation was further complicated if fields were not defoliated when bolls were 60 to 70 percent open. Due to weather complications, many fields were not defoliated until nearly all the bolls were open in the Mid-South this year.”

Another example of the fickleness of Mother Nature happened in Louisiana, noted state Extension cotton specialist John Barnett. “The 2001 Louisiana cotton crop was in excellent condition on Aug. 15, but by Sept. 15, 30 percent or more had been rotted away by the excessive rainfall that occurred in late August and early September.”

On the other hand, Barnett stressed that growers shouldn't underestimate their ability to impact yield and quality. “How you manage your crop can have a definite effect on micronaire and staple — regardless of where you farm, or what variety you plant.”

Cotton specialists point to several major production areas where growers can impact fiber quality and yield, including irrigation, stand, fertility and defoliation.

Irrigation

“The biggest problems come from starting irrigation systems too late, or waiting too long between applications. If you are going to irrigate, it is critical that you be on some kind of management schedule,” Barnett said.

“We recommend the Arkansas Irrigation Scheduler for our region. But you can also place tensiometers in the field or rely on visual inspections. Visual inspections can be misleading, however, and can often cause a late start on irrigation.”

Arkansas Extension cotton specialist Bill Robertson stresses that growers must read the plant and meet its needs while not overdoing it. “Don't irrigate based on the calendar or what happened last year — read the plant and avoid moisture stress particularly early. Avoid over-irrigation.”

“If you irrigate too late in the season, and the crop keeps growing too late, you get a trashier cotton that's harder to defoliate. If you start irrigating too late, on the other hand, you can get hit in three ways. If it's dry during bloom when the fiber length is established, you're going to establish a short length, which will hit you on micronaire and yield too.

“Don't let the plant stress for moisture going into bloom or during bloom. That's a six-week period that goes up until about mid-August.”

Good fertility program

“Soil testing and following recommendations is more important than ever before with the fast-fruiting, early-maturing varieties that we have to work with today,” Barnett said.

“When retention is high, we must be prepared to meet increased moisture and nutritional demand to effectively fill bolls,” Robertson said. “It was a far too common sight this season to see nitrogen-deficient fields. Sample petioles and plan ahead. Once deficient, it is difficult to keep ahead.”

“It goes without saying that cotton's nutrient requirement and pH ranges must be met,” said Mississippi Extension cotton specialist Will McCarty.

Uniform stand

A uniform stand can also impact yield and reduce the possibility of high micronaire problems.

Defoliation/harvest

Defoliation and harvest can be critical components for putting the most cotton possible with the best possible fiber quality into the gin. “Minor modifications in crop termination timing can significantly reduce high-mike discounts,” McCarty said. “Defoliate on time with a product that reduces leaf stick. Pick on time, build modules with dry seedcotton, cover them and place them where water will not stand.”

“A grower must know his land and know the capability of his land — in doing so he can match land to crops. This is a basic premise to being successful in row crop agriculture,” the specialist added. “Cotton must be planted on land that is potentially productive.”

Growers must take care of their land's needs, McCarty added. “Drainage is critical to cotton production — drainage, drainage and drainage — it cannot be overemphasized.”

McCarty also stressed that low-organic-matter soils are prime candidates for rotation with a high-residue crop such as corn. “And corn seems to have similar soil requirements as cotton — well-drained, fertile, etc. Good cotton land will generally be good corn land and vise versa. As organic matter levels go up, so does water infiltration, rooting depth, etc.”

Robertson adds that nematodes can be a silent killer of yield and quality. “Sample, sample, sample — know what you have. Manage each field based on sample results.”